The present invention relates generally to the field of magnetic data storage and retrieval systems. Specifically, the present invention relates to a method of controlling the stripe height of a magnetoresistive (MR) element.
Disc drives are well known in the art and comprise several discs, each disc having several concentric data tracks for storing data. A magnetic read/write transducing head carried by a slider is used to read from or write to a data track on a disc. Such sliders, as well as the transducing heads, are typically produced by using thin film deposition techniques. In a typical process, an array of sliders are formed on a common substrate or wafer. The wafer is typically inspected, and is then sliced to produce bars, with a row of sliders in a side-by-side pattern on each bar. The bars are then lapped at the surface that will eventually face the recording medium to obtain the desired magnetoresistive (MR) element height (also referred to as thee specified stripe height). After lapping, an air bearing pattern is formed on the bars and the bars are diced to produce individual sliders.
With the move to higher areal densities on discs, there is extreme pressure to reduce the stripe height on the sliders. Reducing the stripe height permits an increase in areal densities and signal quality. However, problems emerge as stripe heights drop below one-tenth of a micro-inch. As stripe heights are reduced, seemingly minor variances in the stripe heights from slider to slider will produce different signal amplitudes in each of the sliders. These differing amplitudes make it difficult to control the signal from slider to slider. Thus, though it desired to reduce the stripe heights, it is also desired that the MR elements for each slider on the bar be lapped to the same stripe height.
To achieve reduced stripe heights on the sliders, accurate control of the manufacturing process has become critical. In particular, tight control of the lapping process is required to achieve the finished stripe heights within the desired tolerance on each slider on the bar. Current efforts for controlling the lapping process involves placing one or more lapping sensors on the bar. During the lapping process, material is removed from the surface of the bar. As material is removed from the surface of the bar, material is likewise removed from the lapping sensors attached to the bar. The lapping sensors have a known resistance per unit of thickness so that as the surface of the bar is lapped, the resistence of the lapping sensor changes. The lapping sensors are monitored during lapping to provide feedback to a control system indicating the amount of material being removed from the bar by the lapping device.
Included as part of the control system is a fixture for holding the bar above the lapping mechanism. The fixture, and thus the bar, can be moved relative to the lapping mechanism. The fixture is controlled based on the feedback from the lapping sensors to move the bar and allow the lapping mechanism to remove an amount of material during lapping corresponding to a given resistence of the lapping sensor. Upon achieving the desired resistance of the lapping sensor, it is estimated that the desired stripe heights of the sliders on the bar are also achieved. Once the desired resistence of the lapping sensor is reached, the fixture can be controlled to remove the bar from the lapping device.
These current slider finishing processes lack the accuracy required to achieve the desired reduced stripe heights within the desired tolerance for each slider on the bar. In particular, the lapping sensors provide only a local measure of material removal, so that sliders on a given bar which are located far from the sensor may not be lapped to the appropriate height. In addition, the bar is very long compared to the dimensions of interest, and it is difficult to align the parts in the fixture so that all the sliders are lapped equally. With the desired stripe heights dropping to below 0.1 micrometers, current lapping systems are inadequate.
Thus, there is a continuing need in the art for improved slider lapping systems which allow for tight tolerance control in finishing the stripe heights of sliders on a bar.
The present invention is a method for lapping the MR element on a slider having a shear based transducer. The slider""s shear based transducer is used during the lapping process to more precisely position the portion of the slider carrying the MR element relative to the lapping mechanism. Each slider likewise has a sensor for sensing the stripe height during the lapping process. Based on the sensed stripe height, the shear based transducer can be actuated to move the MR element to a desired position relative to a lapping device. By monitoring the sensed stipe height, the shear based transducer can be controlled to ensure the MR element is precisely lapped to the desired stripe height.